Lupeol acetate as a potent antifungal compound against opportunistic human and phytopathogenic mold Macrophomina phaseolina.

Antifungal activity of Monotheca buxifolia methanolic extract and its various fractions were assessed against Macrophomina phaseolina, a soil-borne fungal pathogen of more than 500 vegetal species as well as rare and emerging opportunistic human pathogen. Different concentrations of methanolic extract (3.125 to 200 mg mL-1) inhibited fungal biomass by 39-45%. Isolated n-hexane, chloroform and ethyl acetate fractions suppressed fungal biomass by 32-52%, 29-50% and 29-35%, respectively. Triterpenes lupeol and lupeol acetate (1, 2) were isolated from n-hexane while betulin, ß-sitosterol, ß-amyrin, oleanolic acid (3-6) were isolated from chloroform fraction. Vanillic acid, protocatechuic acid, kaempferol and quercetin (7-10) were isolated from the ethyl acetate fraction and identified using various spectroscopic techniques namely mass spectroscopy and NMR. Antifungal activity of different concentrations (0.0312 to 2 mg mL-1) of the isolated compounds was evaluated and compared with the activity of a broad spectrum fungicide mancozeb. Different concentrations of mencozeb reduced fungal biomass by 83-85%. Among the isolated compounds lupeol acetate (2) was found the highest antifungal against M. phaseolina followed by betulin (3), vanillic acid (7), protocatechuic acid (8), ß-amyrin (5) and oleanolic acid (6) resulting in 79-81%, 77-79%, 74-79%, 67-72%, 68-71% and 68-71%, respectively. Rest of the compounds also showed considerable antifungal activity and reduced M. phaseolina biomass by 41-64%.

Cross-resistance of the pathogenic fungus Alternaria alternata to fungicides with different modes of action.

BACKGROUND: Cross-resistance, a phenomenon that a pathogen resists to one antimicrobial compound also resists to one or several other compounds, is one of major threats to human health and sustainable food production. It usually occurs among antimicrobial compounds sharing the mode of action. In this study, we determined the sensitivity profiles of Alternaria alternata, a fungal pathogen which can cause diseases in many crops to two fungicides (mancozeb and difenoconazole) with different mode of action using a large number of isolates (234) collected from seven potato fields across China. RESULTS: We found that pathogens could also develop cross resistance to fungicides with different modes of action as indicated by a strong positive correlation between mancozeb and difenoconazole tolerances to A. alternata. We also found a positive association between mancozeb tolerance and aggressiveness of A. alternata, suggesting no fitness penalty of developing mancozeb resistance in the pathogen and hypothesize that mechanisms such as antimicrobial compound efflux and detoxification that limit intercellular accumulation of natural/synthetic chemicals in pathogens might account for the cross-resistance and the positive association between pathogen aggressiveness and mancozeb tolerance. CONCLUSIONS: The detection of cross-resistance among different classes of fungicides suggests that the mode of action alone may not be an adequate sole criterion to determine what components to use in the mixture and/or rotation of fungicides in agricultural and medical sects. Similarly, the observation of a positive association between the pathogen's aggressiveness and tolerance to mancozeb suggests that intensive application of site non-specific fungicides might simultaneously lead to reduced fungicide resistance and enhanced ability to cause diseases in pathogen populations, thereby posing a greater threat to agricultural production and human health. In this case, the use of evolutionary principles in closely monitoring populations and the use of appropriate fungicide applications are important for effective use of the fungicides and durable infectious disease management.

Comparative study of antifungal effect of green and chemically synthesised silver nanoparticles in combination with carbendazim, mancozeb, and thiram.

This study reports synthesis and characterisation of silver nanoparticles and their effect on antifungal efficacy of common agricultural fungicides. Silver nanoparticles were synthesised using biological and chemical reduction methods employing Elettaria cardamomum leaf extract and sodium citrate, respectively. Nanoparticles were then characterised using UV-Visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy, and dynamic light scattering (DLS). While XRD assigned particles size of 31.86 nm for green and 41.91 nm for chemical silver nanoparticles with the help of the Debye-Scherrer formula, DLS specified monodisperse nature of both suspensions. Nanoparticles were tested individually and in combination with fungicides (carbendazim, mancozeb, and thiram) against fungal phytopathogens. Silver nanoparticles exhibited good antifungal activity and minimum inhibitory concentration (MIC) was observed in the range of 8-64 µg/ml. Also, they positively influenced the efficacy of fungicides. The mean MIC value (mean ± SD) for combination of all three fungicides with green AgNPs was 1.37 ± 0.6 µg/ml and for chemical AgNPs was 1.73 ± 1.0 µg/ml. Hence, it could be concluded that green AgNPs performed better than chemical AgNPs. Synergy was observed between green AgNPs and fungicides against Fusarium oxysporum. In conclusion, this study reports synthesis of monodisperse silver nanoparticles which serve as efficient antifungal agents and also enhance the fungicidal action of reported agricultural fungicides in combination studies.

Yield loss assessment due to Alternaria blight and its management in linseed.

Field experiments were conducted during 2010-11 and 2011-12 to assess the yield losses due to Alternaria blight disease caused by Alternaria lini and A. linicola in recently released cultivars and their management with the integration of Trichoderma viride, fungicides and plant extract. Disease severity on leaves varied from 41.07% (Parvati) to 65.01% (Chambal) while bud damage per cent ranged between 23.56% (Shekhar) to 46.12% (T-397), respectively in different cultivars. Maximum yield loss of 58.44% was recorded in cultivar Neelum followed by Parvati (55.56%), Meera (55.56%) and Chambal (51.72%), respectively while minimum loss was recorded in Kiran (19.99%) and Jeevan (22.22%). Minimum mean disease severity (19.47%) with maximum disease control (69.74%) was recorded with the treatment: seed treatment (ST) with vitavax power (2 g kg(-1) seed) + 2 foliar sprays (FS) of Saaf (a mixture of carbendazim+mancozeb) 0.2% followed by ST with Trichoderma viride (4g kg(-1) seed) + 2 FS of Saaf (0.2%). Minimum bud damage (13.75%) with maximum control (60.94%) was recorded with treatment of ST with vitavax power+2 FS of propiconazole (0.2%). Maximum mean seed yield (1440 kg ha(-1)) with maximum net return (Rs. 15352/ha) and benefit cost ratio (1:11.04) was obtained with treatment ST with vitavax power + 2 FS of Neem leaf extract followed by treatment ST with vitavax power+2 FS of Saaf (1378 kg ha(-1)).

Utility of six fungicides for selective isolation of Evlachovaea sp. and Tolypocladium cylindrosporum.

The effects of the fungicides dodine, benomyl, thiabendazole, mancozeb, cupric sulfate, and copper oxychloride were examined in vitro upon germination and further development of Evlachovaea sp. and Tolypocladium cylindrosporum. Fungicidal activity depended on concentrations and varied among products, fungi and the strains tested. Depending on the fungicidal concentration, germination of conidia was induced but germlings produced neither mycelium nor new conidia. There was a good recovery of both Evlachovaea sp. and T. cylindrosporum from previously sterilized soils with fungicide-supplemented medium. Fungi were resistant to copper oxychloride up to 30 g/l, and this fungicide was found to have no utility for a selective medium. Minimal fungicide concentrations for successful isolations were 1 mg/l for benomyl, 200 mg/l for cupric sulfate, 50 mg/l for dodine, 100 mg/l for mancozeb, and 4 mg/l for thiabendazole. Thiabendazole, which is easy to obtain and can be used in low quantities, showed the greatest utility for a selective medium with these entomopathogenic fungi.

Spatiotemporal relationships between disease development and airborne inoculum in unmanaged and managed Botrytis leaf blight epidemics.

Comparatively little quantitative information is available on both the spatial and temporal relationships that develop between airborne inoculum and disease intensity during the course of aerially spread epidemics. Botrytis leaf blight and Botrytis squamosa airborne inoculum were analyzed over space and time during 2 years (2002 and 2004) in a nonprotected experimental field, using a 6 x 8 lattice of quadrats of 10 x 10 m each. A similar experiment was conducted in 2004 and 2006 in a commercial field managed for Botrytis leaf blight using a 5 x 5 lattice of quadrats of 25 x 25 m each. Each quadrat was monitored weekly for lesion density (LD) and aerial conidium concentration (ACC). The adjustment of the Taylor's power law showed that heterogeneity in both LD and ACC generally increased with increasing mean. Unmanaged epidemics were characterized in either year, with aggregation indices derived from SADIE (Spatial Analysis by Distance Indices). For LD, the aggregation indices suggested a random pattern of disease early in the season, followed by an aggregated pattern in the second part of the epidemic. The index of aggregation for ACC in 2002 was significantly greater than 1 at only one date, while it was significantly greater than 1 at most sampling dates in 2004. In both years and for both variables, positive trends in partial autocorrelation were observed mainly for a spatial lag of 1. In 2002, the overall pattern of partial autocorrelations over sampling dates was similar for LD and ACC with no significant partial autocorrelation during the first part of the epidemic, followed by a period with significant positive autocorrelation, and again no autocorrelation on the last three sampling dates. In 2004, there was no significant positive autocorrelation for LD at most sampling dates while for ACC, there was a fluctuation between significant and non-significant positive correlation over sampling dates. There was a significant spatial correlation between ACC at given date (t(i)) and LD 1 week later (t(i + 1)) on most sampling dates in both 2002 and 2004 for the unmanaged and managed sites. It was concluded that LD and ACC were not aggregated in the early stage of epidemics, when both disease intensity and airborne conidia concentration were low. This was supported by the analysis of LD and ACC from a commercial field, where managed levels of disease were low, and where no aggregation of both variables was detected. It was further concluded that a reliable monitoring of airborne inoculum for management of Botrytis leaf blight is achievable in managed fields using few spore samplers per field.

[Testing of seed-borne fungi of Glycyrrihiza seed and disinfection effect of several fungicides on seed-borne fungi].

OBJECTIVE: To study the dominant seed-borne fungi of Glycyrrihiza seeds which were from different producing area and compare the disinfection effect of several fungicides on seed-borne fungi of Glycyrrihiza seed. METHOD: Petri-dish testing was used to determine the external and internal seed-borne fungi and the disinfection effect of fungicides. RESULT AND CONCLUSION: The result showed that the amount of spore on the surface of one Glycyrrihiza seed varied from 0.3% to 37.0% among samples. Penicillium spp. and Aspergillus spp. were the two major dominant fungi and there was few differences in the type of the fungi among producing areas but differences in the isolation frequency of the furgi; Penicillium spp. , Rhizopus spp. , Aspergillus spp. and Alternaria spp. were the internally dominant seed-borne fungi, including seed capsule and the internal tissue of seed and their fungi-carrying percentage was 8.0%-48.3% and 3.5%-42.0% respectively. There were differences in fungi percentage and dominant seed borne fungi among different producing areas. The disinfection effect of both mancozeb and thriam was up to 89.0%, so it is suggested to use them to disinfect Glycyrrihiza seed.

Fungicidal activity of volatile oil from eucalyptus Citriodora Hook. against Alternaria triticina.

Use of plant products for the management of phytopathogenic fungi is fast becoming an important component of Integrated Disease Management (I.D.M.) programme. The natural plant products are bio-degradable and thus eco-friendly, are catching the attention of the scientist worldwide. Such products from higher plants are relatively broad spectrum, bio-efficacious, economical and environmentally safe. Among these essential oils from higher plants because of their greater inhibitory action are being explored preferably worldwide. In this context, a study was undertaken to explore the effect of volatile oil from Eucalyptus citriodora against Alternaria triticina. The radial growth, dry weight and spore germination of pathogen were drastically reduced in response to the different concentrations of volatile oil. A complete inhibition of radial growth, dry weight and spore germination were observed at 1500, 1000 and 100 ppm, respectively. In contrast, similar complete inhibition of test pathogen was observed at very high concentration (6500, 6500 and 1000 ppm) of mancozeb--a commercially available synthetic fungicide. Based on these observations, it was therefore concluded that eucalypt volatile oil has potential to suppress the phytopathogenic fungi.

The effect of foliar application of phosphonate formulations on the susceptibility of potato tubers to late blight.

Foliar sprays of potato plants with phosphonic acid (partially neutralised with potassium hydroxide to pH 6.4) substantially reduced infection of the tubers by Phytophthora infestans, the cause of late blight, in glasshouse and field experiments over a 4-year period. Healthy tubers of blight-susceptible cultivars removed from treated plants and artificially inoculated by spraying with sporangial/zoospore suspensions of P infestans did not develop disease symptoms, demonstrating that the phosphonate applications had directly reduced the susceptibility of tubers to infection, probably as a result of translocation into tuber tissue. In contrast, foliar application of fosetyl-aluminium did not significantly reduce tuber blight development following inoculation. Five to six sprays of partially neutralised phosphonic acid (2 kg ha-1) applied at 10-14 day intervals resulted in the least tuber infection, but such a treatment regime may not be economic. In trials where the effect of timing and rate of application of 2-4 kg phosphonic acid ha-1 was examined, a single treatment of 4 kg ha-1 applied mid- or late-season proved the most effective. A spray programme in which one or two applications of phosphonic acid are combined with use of a non-systemic or systemic fungicide to enhance foliar protection offers the possibility of controlling both foliage and tuber blight and could have a major impact in reducing overwinter survival of P infestans in tubers.

Influence of selenium on the efficiency of fungicide action against certain fungi.

Aspergillus funiculosus was isolated from rotted banana fruits, whereas Alternaria tenuis and Fusarium sp. were isolated from rotted tomato fruits. The isolated fungi tolerated relatively high levels of the fungicide, Dithane, up to 2560 ppm on solid medium, but grew well at 40 ppm when supplemented with liquid medium. They are able to tolerate selenite up to 2% (w/v) sodium selenite. A. funiculosus showed no growth in the presence of mixture of 2.5 ppm selenium and 20 ppm Dithane, whereas Fusarium sp. failed to grow at 2.5 ppm selenium and 10 ppm Dithane, or at 10 ppm of each. Nevertheless, Alternaria tenuis is more tolerant; it showed growth in the presence of relatively high levels of selenium and Dithane; up to 10 ppm selenium and 40 ppm Dithane, however, its growth was inhibited by the presence of a mixture of both. The results suggested new form of highly active fungicides. Selenium as an essential nutrient at such very low concentrations, as well as the application of very low concentrations of the fungicide, would certainly reduce the hazardous effect of such pollutant in the environment.

Inhibitors for the mutagenicities of colon carcinogens, 1,2-dimethylhydrazine and azoxymethane, in the host-mediated assay.

Inhibitory effects of several chemicals on the mutagenicities of 1,2-dimethylhydrazine (DMH) and azoxymethane (AOM) for Salmonella typhimurium G46 in the host-mediated assay were investigated. They were carbon disulfide (CS2), tetraethylthiuram disulfide (disulfiram, DSF), sodium diethyldithiocarbamate (SDDC), ethylene-bis(dithiocarbamato) manganese (Maneb), pyrazole (PZ), aminoacetonitrile hydrogen sulfate (AAN), and sodium selenite (SE). All the compounds, except for SE, inhibited the mutagenicities of DMH and AOM.